Subsea capture system and method of using same

ABSTRACT

A subsea capture system, comprising a plurality of leak sources on a sea floor, the leak sources having a density less than sea water; and a capture device located above the plurality of leak sources, the capture device comprising an internal surface inclined to collect the plurality of leak sources at one more collection points located at a top of the capture device.

This application claims the benefit of U.S. Provisional Application No. 61/378,226 filed Aug. 30, 2010, the entire disclosure of which is hereby incorporated by reference.

BACKGROUND

When oil and gas is spilled into the sea, for example from a leaking tanker ship, a leaking pipeline, from oil seeping from an underground formation, or from oil flowing from a subsea wellhead or blowout preventer, there is a desire to collect the oil and gas and contain and transport or otherwise dispose of the oil and gas to prevent environmental damage to the sea and nearby coastlines. Various systems and methods of collecting spilled oil and gas are known in the art and set forth below:

U.S. Pat. No. 4,405,258 discloses a method for storing a lighter-than-water fluid, e.g., oil, produced from the blowout of an offshore subsea well. The method includes the steps of deploying a containment dome in shallow water near the location of the seabed where the containment dome is to be located. The containment dome as an upper expanded dome-like fluid impervious membrane, a fluid impervious hollow peripheral ring attached to the periphery of the membrane to provide a depending bag-like container, and discrete water drainage means within the bag-like container for connection to pump conduit means therefrom. Wet sand from the seabed is then pumped into the bag-like container, and water is then drained from the wet sand through the water drainage means so as to provide a body of drained sand disposed within the bag-like container and providing a hollow peripheral ring as a hollow peripheral torus acting as a self-supporting structure and as an anchor for the dome-like structural unit. The dome is then charged with a buoyant amount of air and the buoyed dome is floated out to the site where the dome is to be deployed. It is then submerged by controllably releasing the air while substantially simultaneously filling the dome with water, thereby sinking the dome until the lighter-than-water fluid is captured within the dome, while such fluid substantially simultaneously displaces water from within the dome. U.S. Pat. No. 4,405,258 is herein incorporated by reference in its entirety.

U.S. Pat. No. 4,643,612 discloses an oil storage barge having a concave bottom is adapted to be anchored over a subsea well or pipeline that is leaking oil. Flexible skirts extend to the ocean floor, and oil that is trapped under the barge may be stored in the barge or then transferred to another vessel. U.S. Pat. No. 4,643,612 is herein incorporated by reference in its entirety.

U.S. Pat. No. 5,114,273 discloses a protective device installed to or around an offshore drilling platform for oil or gas and the device when in operation to encircle or enclose the platform with a floating containment device and attached oil containment curtain hanging from the device to the ocean floor. The pollution containment device to be submerged normally and activated to the surface when needed. This device will entrap offshore platform pollutants in a short amount of time with a minimum amount of effort and will maintain a clean environment. Other methods of offshore platform pollution containment devices are shown, including permanent non-moving oil pollution containment barriers and activated barriers that operate internally and externally of the oil platform to form an all encompassing barrier from the ocean floor to above the water surface to hold an oil spill to the platform area. U.S. Pat. No. 5,114,273 is herein incorporated by reference in its entirety.

U.S. Pat. No. 5,213,444 discloses an oil/gas collector/separator for recovery of oil leaking, for example, from an offshore or underwater oil well. The separator is floated over the point of the leak and tethered in place so as to receive oil/gas floating, or forced under pressure, toward the water surface from either a broken or leaking oil well casing, line, or sunken ship. The separator is provided with a downwardly extending skirt to contain the oil/gas which floats or is forced upward into a dome wherein the gas is separated from the oil/water, with the gas being flared (burned) at the top of the dome, and the oil is separated from water and pumped to a point of use. Since the density of oil is less than that of water it can be easily separated from any water entering the dome. U.S. Pat. No. 5,213,444 is herein incorporated by reference in its entirety.

U.S. Pat. No. 6,592,299 discloses a method of detecting and locating fresh water springs at sea essentially by taking salinity measurements and by methods and installations for collecting the fresh water. The collection installations comprise an immersed bell-shaped reservoir containing and trapping the fresh water in its top portion, and a pumping system for taking fresh water and delivering the fresh water via a delivery pipe, characterized in that the circumference of the bottom end of the reservoir and/or the circumference of the bottom end of a chimney inside the reservoir and open at its top end and surrounding the fresh water resurgence in part and preferably in full, follow(s) closely the outline of the relief of the bottom of the sea so as to provide leakproofing between the circumference(s) and the bottom of the sea. U.S. Pat. No. 6,592,299 is herein incorporated by reference in its entirety.

There is a need in the art for one or more of the following:

Improved systems and methods for collecting spilled oil and gas from a marine environment;

Improved systems and methods for collecting oil and gas spilling from a subsea well;

Improved systems and methods for collecting oil and gas spilling from a subsurface formation located beneath a body of water; and/or

Improved systems and methods for collecting oil and gas spilling from a subsurface formation located beneath a body of water, and then burning the gas and containing the oil in a surface vessel.

SUMMARY OF THE INVENTION

One aspect of the invention provides a method of capturing subsea leaks, comprising locating a plurality of leak sources on a sea floor, the leak sources having a density less than sea water; installing a capture device above the plurality of leak sources, the capture device comprising an internal surface inclined relative to the sea floor; and collecting the plurality of leak sources at one more collection points located at a top of the capture device.

Another aspect of the invention provides a subsea capture system, comprising a plurality of leak sources on a sea floor, the leak sources having a density less than sea water; and a capture device located above the plurality of leak sources, the capture device comprising an internal surface inclined to collect the plurality of leak sources at one more collection points located at a top of the capture device.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the features and advantages of the present invention can be understood in detail, a more particular description of the invention may be had by reference to the embodiments thereof that are illustrated in the appended drawings. These drawings are used to illustrate only typical embodiments of this invention, and are not to be considered limiting of its scope, for the invention may admit to other equally effective embodiments. The figures are not necessarily to scale and certain features and certain views of the figures may be shown exaggerated in scale or in schematic in the interest of clarity and conciseness.

FIG. 1 is a schematic diagram depicting a wellsite positioned about a subsea reservoir, the wellsite having a containment system in accordance with an aspect of the present invention.

FIGS. 2A-2D are schematic diagrams depicting various versions of a containment tent in accordance with an aspect of the present invention.

FIG. 3 is a flow chart depicting a method of containment.

DETAILED DESCRIPTION

Some embodiments of the invention are shown in the above-identified figures and described in detail below. Embodiments are described with reference to certain features and techniques for containing fluids released into the sea.

FIG. 1:

FIG. 1 is a schematic diagram depicting a wellsite 100 positioned about a subsea reservoir 102. The wellsite 100 is provided with a containment system 101 for capturing fluids released into the sea 103. The wellsite 100 includes a surface structure 104 floating on the sea 103, with a riser 106 extending below it for receiving fluids generated from the reservoir 102. A subsea end of the riser 106 is secured to a suction pile 108 positioned in the sea floor (or mud line) 110. Riser connector 109 is provided to secure the riser 106 in position.

The wellsite 100 is further provided with a blow-out preventer (BOP) 112 positioned at a top end of wellbore 114. The wellbore 114 extends through the subsea floor 110 and into the reservoir 102. The BOP 112 is in fluid communication with the wellbore 114 for receiving the fluids (e.g., gas, hydrocarbons, water, etc.) from the reservoir 102. A manifold 116 may optionally be fluidly connected between the BOP 112 and the riser 106 to facilitate the flow of fluids therebetween. The riser 106 may be, for example, a tubular member for passing fluid received from the BOP 112 and/or manifold 116 to the surface. A trap 117 is provided at the subsea end of the riser 106 to collect fluids and/or solids. A pump 118 may also be provided within riser 106 to selectively draw fluid from the BOP 112 through the riser 106. The manifold 116 and/or pump 118 may be used to manipulate the flow of fluid about the wellsite 100.

Fluid drawn from the reservoir 102 and to the surface via riser 106 may be stored in a surface collector 122. The surface collector 122 may be, for example, a conventional separator that separates components of the fluid, such as gas and liquid. Preferably, the pressure of the fluid is reduced in the collector 122. The remaining fluid may be passed to a vessel 120 via tubing (or off-take line) 126 for transport or storage. The tubing 126 preferably fluidly connects the collector 122 to the vessel 120 for establishing fluid communication therebetween.

From time to time, fluid from the reservoir 102 may escape into the sea 103. For example, a reservoir leak 128 may allow fluid to escape from the reservoir and into the sea 103. In another example, a wellsite leak 130 may allow fluid to escape from the wellsite system 100 and into the sea 103 as fluid is produced from the reservoir 102. In such cases, the containment system 101 may be employed to re-capture fluid released by one or more reservoir/wellsite leaks 128,130.

As schematically shown in FIG. 1, the subsea containment system 101 includes a tent 132 positionable above the reservoir leak 128 or positionable above a number of nearby reservoir leaks, and a subsea collector 134 positionable about the wellsite leak 130. Additional tents 132 and/or subsea collectors 134 could also be connected to manifold 116 and/or other locations about the wellsite 100. In addition, a single tent 132 may be used to collect a number of small leaks located near each other, for example from about 1 to about 100 leak sources, or from about 2 to about 10 leaks. The leak sources may be located within a diameter of about 100 meters, for example a diameter from about 5 meters to about 50 meters, or from about 10 meters to about 25 meters.

The tent 132 and/or subsea collectors 134 may be fluidly connected to riser 106. As shown in FIG. 1, the tent 132 is fluidly connected to the surface separator 122 by a conduit 138. The tent 132 may also be connected to riser 106. The subsea collector 134 is fluidly connected to the manifold 116 and riser 106 via flowlines 136 a-b for passing fluid thereto. The tent 132 may be configured to capture reservoir leaks 128 and/or wellsite leaks 130 to prevent release of reservoir fluids into the sea 103, as will be described more fully herein.

FIGS. 2A-2D:

FIG. 2A is a schematic diagram depicting a wellsite 200 positioned about a subsea reservoir 202. The wellsite 200 has a deepwater containment system 201 a positionable about one or more reservoir/wellsite leaks 228,230 for capturing fluid released from such leaks. The wellsite 200 may have one or more BOPs 212, wellbores 214, surface collectors 222, vessels 220, tubings 226, reservoir leaks 228, and/or wellsite leaks 230 that may be the same as the BOP 112, wellbores 114, surface collector 122, vessel 120, tubing 126, reservoir leak 128 and wellsite leak 130 respectively, of FIG. 1.

The deepwater containment system 201 a includes the collector 222, a funnel tent 232 a and multiple clump weights 252 with tethers 254.

The funnel tent 232 a may have a flexible body extendable over the reservoir/wellsite leaks 128,130. The funnel tent 232 a may be made of a flexible and fluid tight material, such as a fabric, polymer, or other suitable material capable of capturing leaking fluid and passing it to the surface. The funnel tent 232 a may have an opening 250 therein positionable to collector 222 for establishing fluid communication therebetween. The funnel tent 232 a may form a dome or funnel shape, like a circus tent, extending from the collector 222 and toward the subsea floor 210. The funnel tent 232 a may be secured to the subsea floor 210 a distance therefrom by tethers 254 anchored by clump weights 252. Instead of clump weights 252, other anchoring devices that are known in the art can be used, such as driven piles or suction piles.

The collector 222 preferably has an open bottom 256 for receiving the fluid from the reservoir leaks 228 and wellsite leaks 230. The collector 222 may be provided with connectors, seals or other devices (not shown) for securing the funnel tent 232 a in position about the collector 222. The collector 222 preferably is fluidly sealed with the funnel tent 232 a to prevent the release of fluid therebetween and into the sea 203. The collector 222 is then in fluid communication with vessel 220 via tubing 226 to pass the captured fluid thereto.

FIG. 2B shows an alternate containment system 201 b positionable at the wellsite 200. This containment system 201 b includes a collector 222, a funnel tent 232 b, clump weights 252 and tethers 254 which may be the same as the collector 222, the funnel tent 232 a, clump weights 252 and tethers 254 of FIG. 2A. In this configuration, a riser 206 is positioned between the collector 222 and the funnel tent 232 b for passing the fluid therebetween. The riser 206 may be the same as the riser 106 of FIG. 1 for passing fluid to the collector 222.

The riser 206 may extend a distance below the surface collector 222 to reduce the height of the tent above the sea floor 210. The funnel tent 232 b acts as a funnel to capture the fluid from the reservoir leak 228 and wellsite leaks 230, and pass such fluid to the riser 206. The funnel tent 232 b may be connected to the riser 206 in the same manner that the funnel tent 232 a is connected to the collector 222.

In some embodiments, the tent may have a height from about 25% to about 400% of the tent's diameter, or from about 50% to about 200%, or from about 75% to about 150%.

FIG. 2C shows a second alternate containment system 201 c positionable at the wellsite 200. This containment system 201 c includes a collector 222, a funnel tent 232 c, clump weights 252 and tethers 254 which may be the same as the collector 222, funnel tent 232 a, clump weights 252 and tethers 254 of FIG. 2A or FIG. 2B. In this configuration, the funnel tent 232 c is a dome-shaped, and a riser 206 extends from the collector 222 and into the funnel tent 232 c for passing the fluid therebetween. The riser 206 may be the same as the riser 106 of FIG. 1 for passing fluid to the collector 222.

The riser 206 may be positioned a distance above a leak, such as wellsite leak 230 for drawing leaking fluid therefrom, or attached to a collection funnel above a leak, or directly attached to a BOP. As shown in FIG. 2C, the riser 206 is positioned above a BOP 212 for capturing the leaking fluid released therefrom. A manifold 216 (similar to the manifold 116 of FIG. 1) is also provided in fluid communication with the BOP 212 and/or other BOP's for collecting the flow from multiple leak sources for passage into riser 206. Optionally, the BOP 212 may be positioned in fluid communication with the manifold 216. The riser 206 may be positioned above the BOP 212 and/or the manifold 216 for receiving leaking fluids therefrom. In some cases, the manifold 216 may be fluidly connected to the riser 206 for passing leaking fluids from the BOP 212 thereto.

The funnel tent 232 c may be positioned about the riser 206 to capture fluid that the riser 206 does not capture. For example, funnel tent 232 c may extend over reservoir leak 228 and another wellsite leak 230 and/or other leak sources that are beyond the reach of riser 206. The funnel tent 232 b may be connected to the riser 206 in the same manner that the funnel tent 232 b is connected to the riser 206. In this case, inlets 258 may be positioned about the riser 206 and adjacent the funnel tent 232 c for receiving fluid capture by tent 232 c. The inlets 258 may be used to draw the fluid captured by funnel tent 232 c into the riser 206. The funnel tent 232 c and the riser 206 may be used alone or together to facilitate flow of fluid to the collector 222.

FIG. 2D shows a third alternate containment system 201 d positionable at the wellsite 200. This containment system 201 d includes a collector 222, clump weights 252 and tethers 254 which may be the same as the collector 222, clump weights 252 and tethers 254 of FIGS. 2A, 2B, and/or 2C. In this configuration, a slanted tent 232 d is positioned over the reservoir leak 228 and wellsite leaks 230. A funnel 260 and/or a riser (not shown) extends below the collector 222 and above an apex 262 of the slanted tent 232 d for passing fluid from the slanted tent 232 d and to the collector 222.

The slanted tent 232 d may be the same as the funnel tents 232 a-c, except that the slanted tent 232 d has a slanted configuration with no opening therethrough. The slanted tent 232 d has a pair of flat panels 264 positioned at an obtuse angle to each other. The flat panels 264 are positioned above the reservoir/wellsite leaks 228, 230 of the wellsite 200. The obtuse angle of the flat panels 264 directs fluid flowing from the reservoir/wellsite leaks 228, 230 to a raised portion 266 of the slanted tent 232 d and up to the apex 262, as indicated by the directional arrows. The funnel 260 is positioned above the apex 262 to capture the fluids passing out of the apex 262, as indicated by the directional arrows. The slanted tent 232 d may optionally be connected to the funnel 260 in the same manner that the tent 232 b is connected to the riser 206. Optionally, a riser (e.g., 106 of FIG. 1, or 206 of FIGS. 2B and/or 2C) may be positioned between funnel 260 and collector 222. The riser 206 may also be positioned through or adjacent to the slanted tent 232 d for receiving fluids therefrom.

While FIGS. 2A-2D depict specific configurations of a containment system 201 a-d, a tent 232 a-d and certain wellsite equipment (e.g., BOPs 212, collector 222, vessel 220), a variety of equipment may be provided. For example, manifolds, pumps, valving and other devices may be present as part of the wellsite operation and/or as part of the containment system. Additionally, a variety of combinations of the configurations depicted may be used. For example, the slanted tent 232 d of FIG. 2D may be used in combination with the riser 206 of FIG. 2B or 2C. The tent may be of any shape capable of directing fluid from leaks to a surface collector, such as dome, funnel, slanted, lean-to, or other shape. While FIGS. 2A-2D show the bottoms of tents 232 a-d several feet above the mudline, the tent bottoms may be at the mud line and form a fluid seal at the mudline.

In some embodiments, collector 222 may include a collection funnel, a riser, and a surface separator and/or a submerged separator to transport the leak fluids to the surface, and then separate liquids from gases. Suitable collection funnels, risers, and separators are disclosed in co-pending U.S. provisional patent applications 61/376,534, having attorney docket number TH4086; 61/376,542 having attorney docket number TH4085; 61/376,595 having attorney docket number TH4088, which are all herein incorporated by reference in their entirety.

In operation, a tent 232 a, 232 b, 232 c, and/or 232 d may be located above a plurality of subsea leak sources. The tents may be located in a body of water and enclose a volume of water. The leaks may be composed of liquids and gases that are lighter than the water, and that riser in the body of water, and collide with an internal surface of the tent. The internal surface of the tent is impermeable to the liquids, and may also be impermeable to the gases and/or water. The liquids and optionally the gases then rise within the tent to one or more collection points at a top of the tent. Collection devices may be provided at the top of the tent such as a a collection funnel, a riser, a subsurface separator, a surface separator, and/or a storage or transportation vessel.

In some embodiments, the tent 232 a, 232 b, 232 c, and/or 232 d may be made of a flexible sheet material, such as woven polyester, fiber reinforced plastic, polymer sheet such as polyethylene or polypropylene or copolymers, nylon fabric, Dacron fabric, aramid fabric, zylon fabric, or vectran fabric.

In some embodiments, the tent 232 a, 232 b, 232 c, and/or 232 d may be anchored at one or more points at the bottom of the tent with clump weights and tethers, driven piles, suction piles, or other anchoring systems as are known in the art. The top of the tent may be provided with buoyancy, such as buoyancy cans, foam buoyancy modules, a buoyant riser, and/or other buoyancy devices as are known in the art.

FIG. 3:

FIG. 3 is a flow chart depicting a method 300 of deepwater containment. The method involves positioning (380) a containment system (e.g., 101, 201) about a wellsite (e.g., 100, 200). The method 400 may involve extending (382) a tent (e.g., 132, 232 a-d) of the containment system over leaks (e.g., 128, 130) at the wellsite. Fluid from the leaks may be collected (384) in the tent.

The collected fluid may be passed (386) from the tent to a surface collector (e.g., 122, 222). In some cases, the collected fluid may be passed (388) from the tent to the surface collector via a riser (e.g., 106, 206). In some cases, the collected fluid may be passed (390) from the tent to the surface collector via a funnel (e.g., 260). The collected fluid may be separated (392). The collected fluid may be passed (394) from the surface collector to a vessel (e.g., 120, 220) for transport.

The steps of the method may be performed in any order, and repeated as desired.

Illustrative Embodiments

In one embodiment, there is disclosed a subsea capture system, comprising a plurality of leak sources on a sea floor, the leak sources having a density less than sea water; and a capture device located above the plurality of leak sources, the capture device comprising an internal surface inclined to collect the plurality of leak sources at one or more collection points located at a top of the capture device. In some embodiments, the leak sources comprise oil. In some embodiments, the leak sources comprise natural gas. In some embodiments, the internal surface of the capture device is inclined at an angle from 15 degrees to 75 degrees relative to horizontal. In some embodiments, the internal surface of the capture device is inclined at an angle from 30 degrees to 60 degrees relative to horizontal. In some embodiments, the plurality of leak sources comprise from about 3 to about 10 leak sources. In some embodiments, the capture device comprises a major dimension across a base of the device from about 5 meters to about 100 meters. In some embodiments, the capture device comprises a diameter across a base of the device from about 10 meters to about 50 meters. In some embodiments, the capture device comprises a flexible sheet material. In some embodiments, the system also includes a riser connected to the collection point. In some embodiments, the system also includes a separator fluidly connected to the collection point. In some embodiments, a liquid storage vessel fluidly connected to the collection point. In some embodiments, the capture device extends down to and seals with the mudline.

In one embodiment, there is disclosed a method of capturing subsea leaks, comprising locating a plurality of leak sources on a sea floor, the leak sources having a density less than sea water; installing a capture device above the plurality of leak sources, the capture device comprising an internal surface inclined relative to horizontal; and collecting the plurality of leak sources at one more collection points located at a top of the capture device.

It will be understood from the foregoing description that various modifications and changes may be made in the preferred and alternative embodiments of the present invention without departing from its true spirit. For example, one or more wellsites and/or components thereof (e.g., collectors, vessels, BOPS, risers, etc.) may be used in combination with one or more containment systems 201 a-d and/or with one or more funnels, risers, tents or other features, as desired.

This description is intended for purposes of illustration only and should not be construed in a limiting sense. The scope of this invention should be determined only by the language of the claims that follow. The term “comprising” within the claims is intended to mean “including at least” such that the recited listing of elements in a claim are an open group. “A,” “an” and other singular terms are intended to include the plural forms thereof unless specifically excluded. 

We claim:
 1. A subsea capture system, comprising: a plurality of leak sources on a sea floor, the leak source fluids having a density less than sea water; and a capture device located above the plurality of leak sources, the capture device comprising an internal surface inclined to collect the plurality of leak sources at one or more collection points located at a top of the capture device.
 2. The system of claim 1, wherein the leak sources comprise oil.
 3. The system of claim 1, wherein the leak sources comprise natural gas.
 4. The system of claim 1, wherein the leak sources comprise fluid from a hydrocarbon reservoir.
 5. The system of claim 1, wherein the internal surface of the capture device is inclined at an angle from 15 degrees to 75 degrees relative to horizontal.
 6. The system of claim 1, wherein the internal surface of the capture device is inclined at an angle from 30 degrees to 60 degrees relative to horizontal.
 7. The system of claim 1, wherein the plurality of leak sources comprise from about 3 to about 10 leak sources.
 8. The system of claim 1, wherein the capture device comprises a major dimension across a base of the device from about 5 meters to about 100 meters.
 9. The system of claim 1, wherein the capture device comprises a diameter across a base of the device from about 10 meters to about 50 meters.
 10. The system of claim 1, wherein the capture device comprises a flexible sheet material.
 11. The system of claim 1, further comprising a riser connected to the collection point.
 12. The system of claim 1, further comprising a separator fluidly connected to the collection point.
 13. The system of claim 1, further comprising a liquid storage vessel fluidly connected to the collection point.
 14. The system of claim 1, wherein the capture system has a fluid seal or partial seal to the sea floor.
 15. A method of capturing subsea leaks, comprising: locating a plurality of leak sources on a sea floor, the leak source fluids having a density less than sea water; installing a capture device above the plurality of leak sources, the capture device comprising an internal surface inclined relative to horizontal; and collecting the plurality of leak sources at one or more collection points located at a top of the capture device. 